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Oxidation and Reduction Research
Back to Secondary Research ---- To understand what oxidiation and reduction an example of each is needed. An example of an oxidation reaction is: O2(g) + 2Mg(s) > 2MgO In this reaction the Oxygen (O2) is the oxidising agent and the magnesium (Mg) becomes oxidised. An example of a reduction reaction is Fe2O3(s) + 3CO > Fe(s) + 3CO2(g). The carbon monoxide (CO) is the reducing agent; it gains an oxygen atom becoming oxidised. In this reaction iron (III) oxide (Fe2O3) loses oxygen and is reduced. (Kotz, J.C. and Treichel, P., 1999.) In the case of the screaming jelly baby reaction Potassium chlorate (V) is the oxidising agent. (RSC, n.d.) 2KClO3(L) > 2KCl(s)+3O2(g) C12H22O11(s)+12O2(g) >12CO2(g)+11H2O(g) The potassium chlorate decomposes to form potassium chloride and oxygen. The potassium chloride and oxygen causes the sugar in the jelly baby to catch fire resulting in the production of water and carbon dioxide, as well as some left over potassium chloride residue. Due to the heat produced from the jelly babies catching fire the potassium chlorate continues to decompose resulting in the violent and rapid reaction seen. (University of Massachusetts Amherst, n.d.) Oxidation follow the general equation: X+Y => X(n+) +Y(n-) This can be divided into two parts: X=>X(n+)+ne(-) and Y+ne(-)=>Y(n-) X is oxidised, losing n electrons (to Y) to form Xn-Y is the oxidising agent in the process Y is reduced, gaining n electrons (supplied by X) to form Yn–Y is the oxidising agent in the process. (Kotz, J.C. and Treichel, P., 1999.) History and Explaination Oxidation and reduction reactions have been known for centuries; ancient civilisations have used oxidation and reduction to change metal oxides and sulphides to metal. They are usually referred to as a redox reactions due to both oxidation and reduction happening concurrently. One substance becomes reduced, while another becomes oxidised. Oxidation is an increase in the oxidation level of a substance as well as a reduction of the number of electrons. The opposite is true for Reduction: its oxidation level decreases while its number of electrons increases. Oxygen is not required for a redox reaction but substances in the reaction that lose electrons are still classed as being oxidised. Oxidation reactions can be recognised by looking at the charge an atom has. Combining a strong oxidising agent with a strong reducing agent causes a violent reaction, for example an explosion. (Kotz, J.C. and Treichel, P., 1999.) A redox reaction is two half reactions one a reduction, the other an oxidation. There are two rules to balancing redox equations, they are: 1. The charges must balance. 2. The number of electrons lost during the oxidation half-reaction must be equal to the ones gained by the reduction half-reaction. The presence of a reducing agent can be tested for by adding it to acidified Potassium Manganite(VII) solution which causes the solution to decolorise. The same can be done with Potassium Dichromate(VI) solution which causes the solution to turn from orange to green. An Oxidising agent can be tested for by adding it to moist starch iodide paper; this causes the paper to change from white to blue. (Freemantle, M., 1995.) References Freemantle, M., 1995. Chemistry in action. 2nd ed. London: Macmillan Press. Kotz, J.C. and Treichel, P., 1999. Chemistry & Chemical Reactivity. 4th Publishing ed. Florida: Saunders College RSC, n.d. Chemistry for Non-Specialists Course Book: The howling/screaming jelly baby. online 26 February 2014. University of Massachusetts Amherst, n.d. 'Lecture Demonstrations: Chemical Reactions ||:Oxidation/Reduction'. online